Smokeless powder process



Fatented May 1, M45

SMOKELESS POER PROCESS Charles Earnest Silk, Alton, BL, assignor to OlinIndustries, Ina, East Alton, IlL, a corporation of Delaware No Drawing.Application January 1, 1944, Serial No. 516,716

17 Claims.

This invention relates to explosives and particularly to smokelesspowder and provides an improved process of manufacturing sphericalgrains thereof. This application is a continuation in part of my priorcopending application, Serial No. 333,107 filed'May 3, 1940.

' Spherical grains of propellent powder in accordance with U. S. Patent2,027,114 have heretofore been manufactured by a procedure in which alacquer, formed by dispersing a smokeless powder base in a suitablesolvent, was distributed in the form of particles in a non-solventmedium, these particles being subsequently transformed to globules atatmsopheric pressure and hardened, by progressively raising thetemperature and vaporizing the solvent, to form the desired gelatinizedgrains.

An object of the present invention, generally stated, is to provide animproved process for the manufacture of spherical grains of propellentpowder.

Another object of the invention is to provide a process for themanufacture of spherical grains of propellent powder wherein a smallerquantity of solvent is required than heretofore. A further object of theinvention is to provide a process whereby the formation of sphericalgrains of smokeless powder is facilitated and expedited.

Other objects will become apparent to those skilled in the art When thefollowing description is read.

In accordance with the present invention, generally stated, theforegoing objects may be accomplished by distributing particles of alacquer, formed by dispersing a smokeless powder base in a limitedquantity of volatile solvent, in a suitable non-solvent medium, thequantity of solvent utilized being insufficient, at normal atmospherictemperature, to render the lacquer workable to the extent necessary. Thepresent invention contemplates that thelacquer be rendered workture.While the lacquer isbeing rendered and maintained fluid by the combinedaction of solvent and heat (under pressure) the mixture is agitated, soas to cause the particles of lacquer to assume a globular shape. Whenthe particles of lacquer have assumed the desired shape, they are set inthat shape by reducing the pressure on the mixture. The pressurereduction may be accomplished either by venting the sealed vessel inwhich the mixture is being agitated while maintainingthe heat (whichresults in evaporation of the solvent from the formed globules) or bylowering the temperature of the mixture (which rsults in freezing theformed globules). By'either of these methods reduction of pressurewithin the vessel to atmospheric may be accomplished; or the pressurereduction may be interrupted at an intermediate point dependent upon thedegreeof venting or the degree of chilling. In any event, after thepressure hasbeen reduced and the globules are'set, the solvent isfurther removed from the globules, as by distilably fluid bythe-combined action of solvent and heat, and particularly that thetemperature of the mixture be elevated to a point at which the heataugments the action of the solvent in increasing the fluidity of thelacquer particles. In order to prevent neutralization ofthe heat effectby evaporation of the solvent, however, an important aspect of thepresent invention resides in the feature that the pressure on themixture is increased to an extent sufficient to inhibit evaporation ofthe solvent at the temperatures encountered which are higher than thenormal (atmospheric pressure) boiling point of the mixlation.

In accordance with this procedure, therefore,

advantage is taken of the fact that a rise in temperature of a givensolution of a smokeless powder base such as nitrocellulose in a suitablesolvent will be accompanied by a marked decrease inviscosity. Bycarrying out the step of shaping the grains at an elevated pressure itbecomes possible to resort to higher temperatures and thus to reduce theamount of solvent required in the process and also to produce moreperfectly shaped grains of improved uniformity of granulation in ashorter time. In accordance with one embodiment of the invention, by lowering the temperature of the suspension after the particles of lacquerhave become transformed into the desired globular shape, the particlesbecome frozen in the acquired shape and the volatile solvent may beremoved, as by evaporation, from the grains while in suspension withoutimpairing their form. In accordance with another embodiment, the sealedtreating vessel is vented after the particles of lacquer have becometransformed into the desired globular shape and the reduction ofpressure incident to such venting causes the volatile solvent to beremoved from the grains while in suspension. In either vent byevaporation. amounts of solvent were required'and a protracted andcarefully controlled distillation period for the removal of solvent wasnecessary in order to secure grains of the desired shape and.

density.

' guanidine.

and density result even with rapid rates of evaporation of the solvent.

These advantages were not obtainable in the processes'heretofore in usein the manufacture of spherical grains of propellent, powder since thestep of shaping the grains occurred at normal atmospheric pressure andat or slightly above normal atmospheric temperature andthe temperaturethen raised to effect the removal of sol- Acc'ordingly, larger Theprocess of this invention may The base may, for example, consist ofnitrocellulose of any desired degree of nitration, viscose ity, orphysical form or of, amixture of different types or nitrocellulose. Thenitrocellulose may be replaced wholly or in part by other high molecularweight smokeless powder bases, such as nitrostarch, capable of beingdispersed in a volatile solvent and of being'converted to a coherentgelatinized solid on evaporation of the solvent. The smokeless powderbase may also contain other active explosive ingredients such as nitro,

aromatic compounds, for example, diand trinitrotoluene, or nitricacidesters oi polyhydroxy compounds such as nitroglycerin, nitroglycol,nitromannite, and pentaerythritol tetranitrate, or otherexplosiveorganic nitrates or nitro compounds, for example, nitraminessuch as nitrosecuring desired characteristics such as, for example,stabilizers, deterrents, waterproofing agents, and other substancesadapted to produce specific effects.

Although the smokeless powder base employed may be one which has beenbrought to a condi- .tion of stability by previous treatments,thepropowder base, it may be used in the fibrous state,

either after having been stabilized by suitable treatments or as freshlynitrated cellulose which has merely been washed to remove occluded acid.

a The starting material may likewise consist of previously colloidednitrocellulose which 'may have become deteriorated by-the eiTect of lonstorage even to such an extent as to contain decomposed spots ofrelatively high acidity. Simbe applied in the manufactureof'smooth-surfaced spherical grains of any suitable smokeless powderbase.

, quer byevaporation.

non-solvent selected be one which is not substantially miscible with thesolvent selectt- :l.

The solvent used to disperse the smokeless powder base in lacquer formis one which is substantially immiscible with the non-solvent mediumvabove referred to and which is sufllciently volatile as to be readilyremoved from the lac- I Generally, the solvent should have a boilingpoint below or not greatly in excess of 100 C. although solvents ofsome.-

what higher boiling points may at times be suitable. vent medium andnitrocellulose as the smokeless powder base, esters such as ethylacetate, 'iso-' propyl acetate, butyl acetate, or ethyl iormate, or

- water-immiscible ketones such as methyl ethyl I medium other thanwater, solvents such as ace- Other agents may be includedfor tone orether-alcohol may be used, provided they are not substantially misciblewith the non-solvent medium selected.

The amount of solvent most suitable for use in any given instance willdepend largely on the particular smokeless powder base employed and thetemperatureof the'graining operation. For

example, in a case where pyronitrocellulose containing about 12.5%nitrogen is formed into .spherical grains at a temperature of 70-85 C.,

an amount of ethyl acetate equal to IVs-4 times the weight of powderbase may be employed. As a general rule, the lower the viscosity oi thenitrocellulose, the lower the proportion .of solvent need. be. Forexample, with a wood nitrocellulose having a viscosity of about 1'7seconds (Her cules method) advantageous results are accomplished whenthe amount or ethyl acetate employed is 3.65 times the weight of thenitrocellulose, whereas with nitrocellulose having a viscosity of about5 seconds, the proportion of ethyl acetate to nitrocellulose may bereduced to 3- to-l.

powder base, alimited quantity of solvent therefor, and water or othersuitable non-solvent medium, suflicient in amount to permit adequate aitation of the mixture, and preferably having a. protective colloiddispersed therein, are 'mixed at a sufliciently elevated temperaturethat a fluid After agitation for a sumcient period, the particles assumea spherical shape probably largely due to the efi'ect oi. interfacialtension forces.

When this stage has been reached, the pressure on the mixture is reducedeither by venting to ilarly, the raw material may consist of colloidednitrocellulose-nitroglycerin powders.

The medium in which the steps of grain formation and subsequent removalof solvent occur is one which is not a solvent for the smokeless' Waterconstitutes the medium powderbase. which'is preferred as a general ruleand from the economical standpoint for such use. It will be understood,however, that other nonsolvent liq- .uids may at times be useful, forexample, solvent naphtha orchlorinated hydrocarbons such as carbontetrachloride, provided always that the the atmosphere or by rapidlycooling the mixture, which results in setting the globules of lacquer intheir acquired spherical shape, in the one case by reducing theinfluence of heat and in the other case by reducing the influence ofsolvent toward fluidity or the lacquer. Alter the globules are thus setand while still maintained in suspension, additional heat may besupplied to remove solvent from the globules by distillation. In orderto effect substantially complete removal of solvent the temperature maybe gradually increased duringthe distillation peri- When water isemployed as the non-sol- H In order to form the desired globules of thev smokeless powder base lacquer, the smokeless The agitation issufas'mwc od, the pressure upon the mixture during this finaldistillation stage being preferably at or about atmospheric.

It will be understood that other desired ,in-

greclients may be present during the graining op-' station. Where thesmokeless powder base consists of deteriorated or unpurifiednitrocellulose, the treatment is preferably carried out in'the Ipresence of a mild alkaline material, such as calcium carbonate,suflicient to neutralize the excess acidity present in the startingmaterial. Furthermore, the desired amount of stabilizers such asdiphenylamine, or a dialkyldiphenylurea such as methyl centralite,deterrents such as dinitrotoluene or dibutyl phthalate, acceleratorssuch as nitroglycerin, or waterproofing agents may be present in themixture. Protective colloids'such as starch, gum arabic, dextrin, animalglue or bentonite may be utilized to facilitate and control thegranulation process, as disclosed in the said U. 8. Patent 2,027,114. Inorder to control the density of the product, solutes may be utilized asdisclosed in U. S. Patent 2,160,626.

The process may be controlled so that grains of predetermined size anddensity are produced by suitable adjustment of various factors, asdisclosed in the aforesaid U, S; Patent 2,027,114. Thus the averagegrain size may be decreasedby increasing the violence of the agitationor by increasing the amount of protective colloid present,

or by decreasing the viscosity of the smokeless powder base lacquer, asby the use of more solvent or by raising the temperature of the grainingoperation. The average grain size may be increased by changing theserection.

In order to illustrate the process of this invention, a detaileddescription is given below of the practice followed in manufacturingsmooth-surfaced spherical grains of smokeless powder with the use offinely divided nitrocellulose as starting material. This raw materialmay be obtained, for example, by grinding granular colloidednitrocellulose in the presence of water and screening the resultingpowder through a suitable screen, for example, one finer than 8 mesh.

The steps of forming the grains and removing the volatile solvents mayconveniently be carried out in a single vessel provided with thenecessary facilities, such as means for heating and cooling thecontents, for example a suitable jacket through which cooling or heatingfluid may be circulated; suitable means for agitation, such as arotatable shaft on which are. mounted a plurality of horizontallydisposed blades, the action of which may be supplemented by baflleswhich project inwardly from the sides of the vessel; an orifice at thetop for charging the vessel and a cover for sealing the same; an outletat the bottom of the vessel for discharging the contents and a suitablevalve for opening and closing the same; and a vapor outlet leading to acondenser,

furnished with a valve which may be opened or closed at will.

Four hundred pounds of finely divided colloided nitrocellulose in theform of a mud in which the individual particles are finer than 60 mesh,4800 pounds of water, and 4 pounds of finely divided calcium carbonatewere added to a vessel of the above type. This mixture was violentlyagitated by rotating the agitator at a suflicient rate so that thecontents were in a turbulent state and the surface broken up into anumber of vortices. While maintaining the agitation, the temperature ofthe mixture was raised to 50 C. by cirvariables in the opposite difor aperiod of 2 hours at culating hot water through the Jacket. Twelvehundred pounds of ethyl acetate containing 8 pounds of dinitrotolueneand 1 pound of dipbenylamine in solution were then added over a periodof about 45 minutes while the violent agitation was maintained and thetemperature was being raised to C. The vapor outlet 01' the vessel wasthen closed and the contents were heated rapidly to 75 C., the pressurerising to 12.5 pounds per square inch above atmospheric.

At this point the agitation was stopped and the mixture was allowed toseparate into two layers, a bottom aqueous layer, and an upper layer ofnitrocellulose-ethyl acetate lacquer containing droplets of wateremulsified therein. During the stationary separation period of about 15minutes, a solution of 14 pounds of gum arabic in 50 pounds of hot waterwas added to the vessel from a, pressure tank maintained at about 25pounds per square inch pressure above atmospheric.

Violent agitation was then resumed and continued for a brief period, forexample, about 4 or 5 minutes. This resulted in the separation of thelacquer into irregularly shaped particles, each of which wassubsequently to be transformed-into a spherical grain of smokelesspowder. In order to accomplish this transformation of irregularparticles to globules, the mixture was maintained about '75 C. duringagitation sufilcient to maintain the suspension in the freely swirlingliquid while keeping the surface of the liquid smooth and unbroken.

During the grain shaping period, the density 0f-the resulting powdergrains may be controlled in accordance with the process disclosed andclaimed in U. S. Patent 2,160,626. For example, in order to increase thedensity of the product produced in accordance with the present example,a solution containing 75 pounds of sodium sulfate (calculated on thebasis of anhydrous salt) in 400 pounds of water was added under pressureduring the first 15 minutes of the grain shaping period..

When the grains had assumed globular form, the temperature of thesuspension was reduced to C. and the excess pressure above atmosphericwas relieved by opening the vapor line leading to the'condenser. At thistemperature, the lacquer globules became "frozen" form due principallyto the greatly increased viscosity of the lacquer.

The solvent was then removed from the globules by a distillation processin which the temperature was gradually increased, for example, accordingto a schedule in which the temperature'was raised to C. in 45 minutes,then maintained during successive one hour periods at 65-70 C.,'at -75C., and then at -87 0., and finally for minutes at 87-94 C. The waterand,solvent vapor evolved from the suspension were caused to pass atatmospheric pressure through a condenser, the recovered solvent beingsuitable for reuse in the process After removal of the solvent as abovedescribed, the suspension was cooled to room temperature, the powdergrains were recovered by filtration or by means of a centrifuge andwashed with warm water in order to remove the protective colloid andsalt. The grains could then be subjected to a screening operationforseparating the over-sized and under-sized grains from the product.The globular grains of gelatinized nitrocellulose resulting from thisprocedure had a gravimetric density of 0.837 and a majority globules inI in their acquiredf the grains were between 012-024 inch in diameter.

The powder grains at this stage may be subjected to any further desiredprocessing step, for example, to a surface treatment with a modifyingagent such as an accelerator and/or a deterrent. After drying andgraphiting, the powder grains may be stored ready for use.

When a final product having different characteristics is desired, themanufacturing procedure may be varied from the above in order to securegreatest economy of operation. For example, in the production ofspherical grains having an averagediameter of 0.01 inch, more rapidagitation may be employed and a grain shaping period of 30 minutesfollowed by a distillation period of 3-4 hours yield excellent results.

The relatively high fluidity of the lacquer of the smokeless powder baseat the elevated temperature of the graining step causes thetransformation of the dispersed particles of lacquer into globular shapeto occur quite readily, while the increased viscosity of the lacquer atthe lower temperature provided after the graining step imparts to theglobules a marked resistance to deformation during the unavoidablecollisions with other globules, with the agitating means, and with thewalls of the vessel incident to agitation during the step of removingthe solvent.

As illustrating a further embodiment of the invention wherein reductionof pressure upon the mixture after the globules have been formed isaccomplished without chilling but by venting the sealed vesselcontaining pounds of fibrous wood nitrocellulose (containing 13.4%nitrogen) and 41 pounds of finely divided chalk are suspended in 26,000pounds of water and the resulting suspension, after being heated to atemperature of 50-55 C., is

pumped into the distillation vessel. 10,400 pounds of ethyl acetate,containing 33 pounds diphenylamine, are then added to the suspensionduring agitation. The suspension is then heated 'to a temperature of 80C. in about 45 minutes, the vessel being sealed so that a pressure ofabout 15 to 20 pounds per square inch above atmospheric is developed,depending upon the amount of air which is present.

The agitation is discontinued for a period of about 15 minutes,permitting the nitrocellulose solution to coalesce as a separate layerabove the water. During this time, a protective colloid solution isadded, for example a solution of 120 pounds of a good grade animal boneglue in 1500 pounds of water.

Agitation is then resumed, and 15 minutes later a solution of 475 poundsof sodium sulfate in 1500 pounds of water is added. After a total ofabout 2 hours agitation at 80 C., the graining and shaping of globulesis completed.

While the temperature is maintained at 80 C., the outlet valve to thecondenser is gradually opened until a decrease in pressure is noted onthe pressure gauge. The pressure decreases to about 5 pounds per squareinch gauge in about to minutes, venting of air accounting for most ofthis pressure drop. The distillation of solvent starts at this point andcontinues for a period of about .60 minutes, the pressure in thedistillation vessel being reduced gradually to atmospheric by furtheropening the outlet valve to the condenser at intervals. About 80% of thesolvent is removed during this time.

While the above described gradual decrease of pressure canbeaccomplished by careful inch in diameter and 12% being larger than i sthe solvent.

the mixture, 3300 manual operation of the outlet valve, it is generallypreferable to provide automatic pressure release according to apredetermined schedule.

The. temperature of the suspension is then raised to about C. in 45minutes and maintained at this point for about 15 minutes to completethe solvent removal treatment. After cooling, the charge maybecentrifuged, washed, and screened and subjected to any other finishingtreatment that may be desired.

The product of the foregoing process consists of globular grains ofgelatinized nitrocellulose, displaying a gravimetric density of .930 andof which about 74% have a diameter between 0.010 and 0.025 inch, 14%being smaller than 0.010

0.025' inch in diameter. a

In the manufacture of globular smokeless powder grains, in accordancewith the present invention economy is secured not only by virtue of thereduction in the amount of solvent required but also because a shorterperiod is required for forming the grains and for removing Likewise, therate of solvent removal may be much higher than for globules whichcontain a much higher proportion of solvent, since due to the reducedshrinkage obtained on removing solvent from globules which initiallycontain a high solids content, there is less danger of deforming thegrains by shrinkage thereof. The process of this invention, due to thelatter factor, is particularly suited for the production of densegrains.

It will be understood tha an important aspect of my improved process isthe carrying out of the step of graining, or globule formation, at

pressures substantially above'atmospheric which makes it possible toutilize temperatures sufllciently high that the heat contributes towardincreasing the fluidity of the lacquer, without, however, depleting'thelacquer of solvent. The graining step is followed by lowering of thepressure, whichmay or may not be attended by a lowering in temperature,in order to set the grains in their acquired form, and finally, theresidual volatile solvent may be substantially removed, as byevaporation. The operating details hereinbefore described are to beconsidered as illustrative of the invention and not limitative, and manyvariations may be made within its spirit and scope as will be realizedby those skilled in the art when the present description is read. Suchvariations may include, for example, the utilization of other smokelesspowder bases, other solvents, and other suspension media, ashereinbefore described, as well as changes in the temperatures,concentrations, and times of treatment which are subject to adjustmentto give the most desirable results in each particular instance.

Having now described the invention, what is claimed as new and isdesired to be secured by Letters Patent, is:

1. In the art of making explosives, the process comprising, agitatingnitrocellulose and 1 to 4 times its weight of a water-immiscible solventtherefor in an aqueous bath, heating the mixture to 70-85 C. duringagitation without removal oi solvent to form a suspension of fluidparticles oi nitrocellulose solution, continuing the agitation under thesaid conditions to form the said particles into globular shape, andcooling the suspension to about 60 C. to rigidify the said globules.

2. In the art of making explosives, the proces: comprising, suspendingparticles of smokeles:

powder base solution in a non-solvent liquid at an elevated temperaturesufficiently high to render the solution fluid, said non-solvent liquidbeing substantially immiscible with the solution agitating thesuspension while avoiding the removal of solvent from the solution toform globules thereof, then cooling the suspension to rigidify the saidglobules, and thereafter removing solvent.

3. In the art of making explosives, the process comprising, agitating asmokeless powder base in a non-solvent liquid with solvent which isimmiscible with and has a lower boiling point than 7 comprising,agitating a. smokeless powder base in a non-solvent liquid, addingsolvent substantially immiscible with the liquid in an amount insufi- Qcient to render the said base fluid at the temperature of admixture butsufficient therefor at a higher temperature, heating the mixture to thesaid higher temperature while concurrently com- ,porting th temperatureand pressure of themixture with the vapor pressure of the solvent tosubstantially avoid removal of solvent from the solution, continuing theagitation under the said conditions to form globules of the solution,and then cooling the suspension to rigidify the said globules.

5. In the art of making xplosives, the process comprising, agitating asmokeless powder base in a non-solvent liquid with solvent which isimmiscible with and has a lower boiling point than the liquid, thesolvent being insuficient in amount to render the said base fluid atbelow the boiling point of the mixture but suflicient therefor at ahigher temperature, heating the mixture in a sealed vessel, to above thenormal boiling point of the mixture, continuing the agitation under thesaid conditions to form globules of smokeless powder base solution, andthen cooling the suspension below the boiling point of the mixture torigidify the said globules,

6. In th art of making explosives, the process comprising, agitating asmokeless powder base in a non-solvent liquid with solvent which isimmiscible with and has a lower boiling point than the liquid, thesolvent being sufiicient in amount to render the said base fluid at atemperature above the boiling point of the mixture, heating the mixturein a sealed vesse to the said temperature and to a pressure aboveatmospheric, continuing the agitation under the said conditions to formglobules of smokeless powder base solution, and thereafter removingsolvent at atmospheric pressure.

7. The process. of claim 2, in which the smoke.- less powder baseconsists of nitrocellulose.

8. The process of claim 2, in which the smokeless powder base consistsof nitrocellulose-nitroglycerin.

9. The process of claim 2, in which the smokeless powder base consistsof nitrostarch.

10. In the art of making explosives, the process comprising, agitatingnitrocellulose and about three times its weight of a water-immisciblesol vent in an aqueous bath, heating the mixture to substantially 75 C.during agitation to form a suspension of fluid particles ofnitrocellulose solution, continuing the agitation under the saidconditions to form globules of the solution, concurrently with saidheating and agitation comporting the temperature and pressure of themixture with the vapor pressure of the solvent to substantially avoidremoval of solvent and cooling the suspension to about60 C. to rigiditythe said globules.

11. In the art of making explosives, the process comprising, agitating asmokeless powder base in a non-solvent liquid with solvent which isimmiscible with the liquid, the solvent being insufllcient in amount torender the said base fluid at an intermediate temperature aboveatmospheric but suflicient therefor at a higher temperature, heat ingthe mixture to the said higher temperature,

continuing .the agitation under the said conditions to form globules ofthe solution, concurrently with said heating and agitation comportingthe temperature and pressure of the mixture with the vapor pressureof'the solvent to substantially avoid removal of solvent and thencooling the suspension to the said intermediate temperature to rigidifythe said globules.

12. Iii the art of making explosives, the process comprising, agitatinga solution of smokeless powder base in a non-solvent liquid, the solventfor saidsolution being immiscible with the liquid, the solvent beingsufllcient in amount to;

render the said base fluid at a temperature above the normal boilingpoint of the mixture, heating the mixture in a sealed vessel withconcomitant increase in pressure to a temperature above the normalboiling point of the mixture, continuing the agitation under saidconditions to form globules of smokeless powder base solution, thenreducing the pressure in the vessel while agitation continues.

13. In the art of making explosives, the process comprising, agitating asolution of smokeless powder Jase in a non-solvent liquid the solventfor said solution being immiscible with andhaving a lower boiling pointthan the liquid, the

solvent being suflicient in amount to render the said base fluid at atemperature above the atmospheric pressure boiling point of the mixture,heating the mixtur in a sealed vessel with concomitant increase inpressure to a temperature above the boiling point of the mixture atatmospheric pressure, continuing the agitation under said conditions toform globules of smokeless powder base solution, then reducing thepressure in the vessel while agitation continues, and thereafter underreduced pressure distilling solvent from the mixture.

14. In the art of making explosives, the process comprising, agitating asolution of smokeless powder base in a non-solvent liquid, the solventfor said solution being immiscible with and having a lower boilingpointv than the liquid, the solvent being suflicient in amount to renderthe said base fluid at a temperature above the atanon-solvent liquidwithsolvent which is immisto render cible with and has a lower boiling p intthan the liquid, the solvent being suflicient i amount ilcient inamountto render said base fluid at atmospheric temperatures, heating.the mixture under pressure above atmospheric to a temper-- ature abovethe atmospheric pressure: boiling point of the mixture, continuing theagitation under the said conditions toform globules or smokeless powderbase solution, and thereafter,

under reduced pressure, distilling solvent'from ;the mixture. v a V v16. In the art of making explosives, the proc-' the said base, fluid ata temperature above the boiling point of the mixture, but insu'I- cancomprising, agitating nitrocellulose powder in a bath of water withethyl acetate there beingapproximately 3 to 4 parts, by weight,

.oi ethyl acetate to each part 01' base powder, concurrently agitatingand heating the mixture in a sealed vessel to atemperature of about 80C. with concomitant increase in pressur'e to about 15 .to 20 pounds persquareinchabove atmospheric pressure, without reducing the temperatureancipiessure discontinuing the agitation for a time sufllcient to permitthe base powder solution to coalesce, resuming the agitation andcontinuing the same until the smokeless powder base solution isdispersed as globules in the water, all without reducing the temperatureor pressure upon'the mixture, then gradually reducing the pressurewithin the vessel to vbetween zero and 5 pounds per square inch aboveatmospheric while maintaining the temperature,

and continuing the heating at such reduced pressure-until the ethylacetate is substantially removed from the globules. v r g 17. In the artoi making explosives, theprocess comprising, suspending particles ofsmokeless powder base. solution in a non-solvent liquid at an elevatedtemperature above the normal boiling point or the mixture to render thesolution fluid,said non-solvent liquid being substan-V tially immisciblewith the solution agitating the suspension under pressure while avoidingthe removal of solvent from the solution to form globules thereof, thenreducing the pressure while agitation continues.

, CHARLES EARNEST SILK.

